The present invention generally relates to a vehicle wheel suspension system and, more particularly, to an independent rear wheel suspension for motor vehicles.
The Japanese Laid-open Patent Publication laid open to public inspection under No. 49-26921 in 1974 discloses a vehicle rear wheel suspension of a construction shown in FIG. 1 of the accompanying drawings. Referring to FIG. 1 of the accompanying drawings, wherein the only left-hand rear wheel and its suspension are diagrammatically shown as viewed from top of a vehicle, the prior art rear wheel suspension comprises a wheel carrier 1 having a wheel journal for the support of a rear wheel 2 for rotation independently of the wheel carrier 1 and operatively coupled to a vehicle superstructure, particularly, a chassis 4, by means of an arm member 3 which extends in a direction generally transversely of the vehicle superstructure and is operatively interposed between the wheel carrier 1 and the chassis 4. The arm member 3 is comprised of a stub 3a and a pair of forked front and rear arms 3b and 3c, it being understood that the terms "front" and "rear" referred to above and hereinafter throughout the specification and the appended claims are used to denote respective positions defined in terms of the vehicle superstructure. The stub 3a has a free end hingedly and yieldingly connected to a lateral portion of the chassis 4 while respective free ends of the front and rear arms 3b and 3c, which are forked from the stub 3a, are hingedly and yieldingly connected at A and B to front and rear portions of the wheel carrier 1 by the intervention of associated rubber bushings. The prior art rear wheel suspension further comprises a tension rod 5 having one end hingedly and yieldingly connected to a front portion of the chassis 4 and the other end hingedly and yieldingly connected to a portion of the arm 3b adjacent the wheel carrier 1.
The prior art rear wheel suspension of the construction shown in FIG. 1 involves such a disadvantage that the wheel 2 tends to toe out particularly during the cornering of the vehicle, that is, during the turn of the vehicle in a direction either leftwards or rightwards. More specifically, during the cornering of the vehicle along a curve, the outer wheel rotates on or follows a larger radius than the inner wheel with the increased pressure of contact of the outer wheel on the road surface while the vehicle superstructure tilts laterally under the influence of centrifugal force and, at this time, the various elastic bushings used at the various joints of the arm member 3 are elastically deformed to such an extent as to increase the tendency of the wheel to toe out. This results in an over-steerability, that is, the steering stability is adversely affected. This equally happens even when the wind blows the vehicle in a direction transversely of the vehicle during the running of the vehicle.
A rear wheel suspension wherein the front and rear arms, corresponding to the arms 3b and 3c shown in FIG. 1, extends from the wheel carrier in substantially parallel relation to each other to different lateral portions of the vehicle chassis is also well known and is disclosed, for example, in the Japanese Patent Publication No. 51-21494, published for opposition on July 2, 1976. Even this rear axle suspension of a type disclosed in the Japanese Patent Publication involves disadvantages similar to that described in connection with the rear wheel suspension of the construction shown in FIG. 1.
The rear wheel suspension wherein the front and rear arms, which are separate from each other, have different lengths and extend in parallel or approximately parallel relation to each other is disclosed in the U.S. Pat. No. 3,759,542, patented on Sept. 18, 1973. With the construction disclosed in this U.S. patent, for a slight displacement of the wheel, the tendency of the wheel to toe in is small. Where the amount of the toe-in of the wheel is desired to be increased, the difference in length between the front and rear arms must be large for a limited space available for the installation of the axle suspension.